This radiation freak out reality check is courtesy of GOOD magazine. Here's the heart of it.:

For anyone terrified that radiation from Japan is coming to cause devastation in America, something the chairman of the Nuclear Regulatory Commission has already called "very unlikely," keep an eye on this real-time radiation detector courtesy of EnviroReporter.com.

According to EnviroReporter, the detector is located in the organization's Santa Monica office (that's right next to the beach, for out-of-towners) "approximately one meter off the ground in a wood-floored structure with built over crawlspace with soil foundation."

What the detection unit is measuring is the Counts Per Minute of iodizing radiation, which EnviroReporter says is between 40 and 46 CPM for their site. Some sites have higher normal background CPM, while others are much lower. And when you're on a plane, the CPM level can climb up to 200 for hours at a time.